Abstract
The purpose of this cross-sectional study was to assess the 2009 prevalence of chlamydial (CT) and gonococcal (GC) infection in two populations in a mid-western city in the United States: patients at a public sexually transmitted disease (STD) clinic, and individuals seeking HIV counseling and testing services at an AIDS community organization. We characterized STD prevalence in a random sample of 592 STD clinic patients and a convenience sample of 471 individuals agreeing to STD testing through outreach efforts at the community organization. The STD clinic population was 59% male, 60% black, with 3.1 mean sex partners in the last year. The community organization population was 72% male, 19% black, with a mean of 4.3 partners in the last year. The prevalence of CT and GC combined was consistently higher in STD clinic patients than at the community organization (18% vs. 4%). CT prevalence was higher than GC prevalence in both populations (CT: 3% and 13% at the STD clinic and community organization, respectively, vs. GC: 1% and 7%, respectively). Factors significantly associated with increased odds of GC/CT at the STD clinic include unmarried status, younger age, at least six partners in the last year, and unprotected sex in the last year. At the community organization, the only factor significantly associated with increased odds of GC/CT was lower educational attainment. Our findings confirm that STD prevalence differs widely by population group. Given these differences, local approaches to STD control should also be carefully targeted to specific subgroups.
Keywords: chlamydia, gonorrhea, STD clinic, NAAT
INTRODUCTION
A 13-year-old report from the Institute of Medicine concludes that “STDs [sexually transmitted diseases] are hidden epidemics of enormous health and economic consequence in the United States. They are hidden because many Americans are reluctant to address sexual health issues in an open way and because of the biologic and social characteristics of these diseases.”1 Despite the passage of more than a decade since the release of that report, its conclusions remain depressingly current. The prevalence of chlamydia and syphilis infections in the United States (US) have increased since 2000;2 racial disparities in STD rates persist;2 and new threats to STD control have emerged, including resistance to widely-used antibiotics.3–4 The news is not all bad: the US Food and Drug Administration approved the first STD-prevention vaccine in the human papillomavirus vaccine Gardasil in 2006,5 and while still highly pervasive, the seroprevalence of herpes simplex virus appears to be slowly declining.2 Nevertheless, researchers from the US Centers for Disease Control and Prevention recently estimated that STD prevalence (including infection with Neisseria gonorrhoeae (GC), Chlamydia trachomatis (CT), Trichomonas vaginalis, herpes simplex virus type 2, or human papillomavirus) was 37.7% among sexually-experienced American adolescents aged 14–19.6
The US STD epidemic remains hidden for a number of reasons – including, for example, lack of access to care for high-risk individuals,7 stigma associated with seeking care for STD symptoms,8–9 missed opportunities for screening and testing at-risk patients10–11 and patient confidentiality concerns.12 Public STD clinics, which typically use a sliding-scale fee for services, serve as a national safety net for STD screening and treatment. The STD clinic in the mid-western US city where the current research was conducted is part of the city’s public health department. Despite high volume (~10,000 patient visits per year), very little data has been published related to STD prevalence within this clinic population or other population groups in this city.
In order to target future STD prevention efforts, we undertook the analyses presented here to measure the 2009 prevalence of urethral chlamydial and gonococcal infection in two distinct but high-risk populations. We assessed GC and CT prevalence among patients directly seeking care at the public STD clinic, and we similarly measured GC and CT prevalence among a separate population of individuals coming for voluntary HIV counseling and testing at a local community AIDS service organization. The overall STD clinic population was expected to be majority African-American, with lower education, younger age, and to report predominately heterosexual partnerships. The population of the community organization was expected to be more highly educated, older, majority white, and with many patients (particularly males) reporting same-sex partnerships.
METHODS
This cross-sectional study assesses the prevalence of gonococcal and chlamydial infection in 2009 in two patient populations in a mid-western US city: a random sample of individuals seeking care at the public STD clinic of the city health department and a convenience sample of individuals at a community AIDS service organization who were approached by STD clinic outreach staff and offered STD testing. We sought to investigate the differences in demographic, behavioral and clinical characteristics between the two populations, and to quantify the correlations between these factors and prevalence of chlamydial and gonococcal infections. Our goal was to identify patient characteristics most strongly associated with STD prevalence in order to target future outreach and screening efforts.
Study populations
STD clinic
From the complete electronic medical record database containing approximately 10,000 STD patient visits from calendar year 2009, we compiled a list of all relevant visits for these analyses. “Relevant” encounters included all visits at the STD clinic where biological specimens were collected and tested for chlamydial (CT) and gonococcal (GC) infection, and excluded follow-up visits where only treatment was administered. We then further limited the database to patient encounters occurring at the STD clinic on the 49 dates when outreach efforts were simultaneously occurring at the community AIDS service organization to yield a sample of 1759 patient visits. Using SAS’s pseudo-random number generator, we then randomly selected 600 of these STD clinic visits for chart abstraction and data entry.
Community AIDS service organization
The community AIDS service organization is a community-based, non-profit AIDS service organization providing comprehensive care services, case management, educational programs and an HIV testing program. As part of its community outreach mission, and in partnership with the community organization, program staff from the STD clinic approach clients at the community organization who have come for HIV testing to offer GC and CT testing. Program staff from the STD clinic perform these outreach efforts approximately once weekly on pre-specified days. Individuals at the community organization who indicate that they would like to be tested for GC and CT provide a urine sample that day, which is subsequently tested in the STD clinic laboratory. During 2009, 487 individuals accessed through outreach efforts at the community organization received GC and CT testing.
Data extraction
Any individual reached through the community organization who consented to STD testing technically became a patient of STD clinic and thus had a unique electronic medical record in the STD clinic system, just like patients who came directly to the clinic for STD testing. From April through June 2010, for each of the 600 randomly selected 2009 visits at the STD clinic and for each of the individuals reached through outreach at the community organization, we abstracted selected data on demographics (year of birth; gender; race; education; type of housing; number in household; marital status), behaviors in the past year (any oral, vaginal or anal sex with men or women; any sex with partners who were HIV-positive, of unknown HIV status, anonymous, or intravenous drug users; any transactional sex; any sex without a condom; and number of sex partners) and clinical data (history of HIV testing and past results; current chlamydial and gonococcal infection status).
Laboratory testing
GC and CT testing was performed on urine samples. Testing for both STD clinic patients and community organization patients was performed at the STD clinic laboratory. GC and CT infection was assessed using nucleic acid amplification testing (NAAT) on the APTIMA Combo 2 platform (Gen-Probe Inc., San Diego).
Ethical approval
The STD clinic is an official research site of The Ohio State University (OSU). OSU’s Institutional Review Board reviewed the protocol and deemed the research exempt from IRB review. OSU’s Privacy Board separately granted a waiver of the requirement for HIPAA Research Authorization.
Data analysis
All statistical analyses were performed in SAS (Version 9.2, Cary, NC).
We first assessed the frequencies of each demographic, behavioral, and clinical factor in the two patient populations. We used chi-square statistics to compare categorical variables, Student’s T-test to compare means, and the Wilcoxon-Mann-Whitney test to compare medians between the two populations.13 We examined GC and CT prevalence by site, gender and by same- and opposite-sex sexual activity. Finally, we ran unadjusted logistic regression models to assess the odds of prevalent GC or CT infection (combined outcome) according to several independent variables. Although we had originally planned to stratify by site and run multivariable regression models to assess the odds of GC/CT infection and simultaneously adjust for several independent variables, the complex interaction between gender and sexual practices in this population prohibited such a model from converging. Thus we present only unadjusted estimates for the association between each demographic or behavioral variable and GC/CT prevalence.
RESULTS
Of the 600 visits randomly selected from STD clinic’s 2009 visits, one was a duplicate record and 7 additional visits (1%) lacked valid GC and CT results and were therefore excluded. Of the 487 individuals at the community organization who agreed to STD testing, 16 (3%) lacked valid GC and CT results. Thus, the final analysis dataset included 1063 individuals: 592 (56%) from the STD clinic and 471 (44%) from the community organization.
Demographic characteristics
Demographic characteristics differed between the two locations. Individuals from the community organization were more likely to be male (72% vs. 59% at the STD clinic, P<0.001), more highly educated (37% college graduates vs. 12% at the STD clinic, P<0.001), and more likely to be white (75% vs. 29% at the STD clinic, P<0.001). Individuals from the community organization had a higher mean and median number of sex partners in the last year (4.4 vs. 3.1 mean partners, P<0.001; 3.0 vs. 2.0 median partners, P<0.001). Mean age was similar between the two groups: 30.1 years among community organization participants and 29.4 years among STD clinic patients (P=0.21) (Table 1).
Table 1.
Selected demographic characteristics of patients at a public STD clinic (n=592) and a community AIDS service organization (n=471) in a mid-western US city, 2009.
| Characteristic | Community organization | STD clinic | P-value | Total | |||
|---|---|---|---|---|---|---|---|
|
|
|
||||||
| n=471 | (%) | n=592 | (%) | n=1063 | (%) | ||
| Gender | <0.0001 | ||||||
| Male | 341 | (72) | 351 | (59) | 692 | (65) | |
| Female | 127 | (27) | 241 | (41) | 368 | (35) | |
| Transgendered | 3 | (1) | 0 | (0) | 3 | (0) | |
| Race | <0.0001 | ||||||
| Black | 90 | (19) | 357 | (60) | 447 | (42) | |
| White | 351 | (75) | 170 | (29) | 521 | (49) | |
| Asian | 12 | (3) | 6 | (1) | 18 | (2) | |
| Hispanic | 8 | (2) | 33 | (6) | 41 | (4) | |
| Other | 10 | (2) | 22 | (4) | 32 | (3) | |
| Marital status | <0.0001 | ||||||
| Divorced, separated or widowed | 38 | (8) | 58 | (10) | 96 | (9) | |
| Married | 15 | (3) | 36 | (6) | 51 | (5) | |
| Single | 353 | (75) | 477 | (81) | 830 | (78) | |
| Missing | 65 | (14) | 21 | (4) | 86 | (8) | |
| Education | <0.0001 | ||||||
| None | 0 | (0) | 2 | (0) | 2 | (0) | |
| Elementary | 2 | (0) | 10 | (2) | 12 | (1) | |
| Some high school | 16 | (3) | 109 | (23) | 125 | (12) | |
| High school graduate/GED | 109 | (23) | 187 | (32) | 296 | (28) | |
| Some college | 98 | (21) | 193 | (33) | 291 | (27) | |
| College graduate | 174 | (37) | 70 | (12) | 244 | (23) | |
| Missing | 72 | (15) | 21 | (4) | 93 | (9) | |
| Age | 30.1 | 10.0 | 29.4 | 10.2 | 0.21 | 29.7 | 10.1 |
| # of sex partners in last year a | 4.3 | 4.4 | 3.1 | 3.5 | <0.0001 | 3.6 | 3.9 |
Abbreviations: STD = sexually transmitted disease; AIDS = acquired immune deficiency syndrome; GED = General Equivalency Diploma; SD = standard deviation
Data missing for n=95 community organization participants (20%) and n=29 STD clinic participants (5%)
HIV testing and prevalence
Data on past HIV testing was available from 83% of individuals from the community organization and 96% of STD clinic patients. Among those with non-missing data, more individuals at the community organization (81%) than at the STD clinic (72%) reported a past HIV test (P=0.005). Self-reported HIV prevalence was similar (2%) in the two populations.
Behavioral characteristics
The frequencies of various self-reported sexual risk behaviors, stratified by gender, are presented in Table 2. At the time of STD testing, clinicians typically asked patients a series of behavioral risk questions. This set of questions was not asked of 15% (n=74; 20 women and 54 men) of the community organization sample and 2% (n=11; 4 women and 7 men) of the STD clinic sample; thus, these individuals are missing from Table 2. For ease of presentation, we also exclude three transgendered individuals from our gender-specific results.
Table 2.
Behavioral risk characteristics of patients at a public STD clinic and a community AIDS service organization in a mid-western US city, 2009.
| Risk behavior | Community organization a | STD clinic a | ||||||
|---|---|---|---|---|---|---|---|---|
|
| ||||||||
| Men = 287 | Women = 107 | Men=344 | Women = 237 | |||||
|
| ||||||||
| n | (%) | n | (%) | n | (%) | n | (%) | |
| In the last year have you ever had vaginal or anal sex … | ||||||||
| With a woman | 87 | (30) | 16 | (15) | 286 | (83) | 18 | (8) |
| With a man | 199 | (69) | 98 | (92) | 44 | (13) | 229 | (97) |
| With an IV drug user | 1 | (0) | 2 | (2) | 2 | (1) | 2 | (1) |
| With a person of unknown HIV status | 104 | (36) | 41 | (38) | 38 | (11) | 28 | (12) |
| With an HIV-positive person | 23 | (8) | 1 | (1) | 5 | (1) | 1 | (0) |
| With an anonymous partner | 86 | (30) | 14 | (13) | 46 | (13) | 13 | (5) |
| With a sex worker | 8 | (3) | 2 | (2) | 6 | (2) | 2 | (1) |
| While using alcohol or drugs | 114 | (40) | 36 | (34) | 115 | (33) | 52 | (22) |
| Without a condom | 165 | (57) | 74 | (69) | 247 | (72) | 168 | (71) |
| In the past year, have you … | ||||||||
| Had oral sex with a woman | 70 | (24) | 16 | (15) | 219 | (64) | 20 | (8) |
| Had oral sex with a man | 202 | (70) | 81 | (76) | 42 | (12) | 163 | (69) |
| Used IV drugs | 2 | (1) | 1 | (1) | 3 | (1) | 2 | (1) |
| Shared drug equipment | 0 | (0) | 0 | (0) | 0 | (0) | 1 | (0) |
| Exchanged sex for drugs or money | 2 | (1) | 2 | (2) | 1 | (0) | 4 | (2) |
Abbreviations: STD = sexually transmitted disease; AIDS = acquired immune deficiency syndrome; IV = intravenous; HIV = human immunodeficiency virus
Excludes 77 individuals from the community organization (74 with missing data on behavioral risk and 3 transgendered individuals) and 11 individuals from the STD clinic (all missing behavioral risk data).
Considering male patients, those in the community organization sample were more likely to report anal sex with a man (69% vs. 13% of men at the STD clinic) and oral sex with a man (70% vs. 12%) in the last year. Less than a third of men from the community organization (30%) reported sex with a woman in the last year, compared to 83% of men at the STD clinic. Men from the community organization were also more likely to report sex in the last year with a person of unknown HIV status (36% vs. 11% of men at the STD clinic), with an HIV-positive person (8% vs. 1% of STD clinic men), and with an anonymous partner (30% vs. 13%). A substantial minority of men in both samples reported sex in the last year while using alcohol or drugs (40% of men at the community organization and 33% at the STD clinic) (Table 2). Men from the community organization were less likely to report any sex without a condom in the last year (57%) than men from the STD clinic (72%).
Women from the community organization were also more likely than their female STD clinic counterparts to report same-gender sexual activity: 15% of women at the community organization vs. 8% of women at the STD clinic reported sex with a woman in the last year. The majority of women from both sites reported sex with a man in the last year (92% of women from the community organization and 97% of women from the STD clinic). Women from the community organization were more likely than women from the STD clinic to report sex with a person of unknown HIV status (38% vs. 12% of women at the STD clinic) and with an anonymous partner (13% vs. 5% of STD clinic women). Sex while using drugs or alcohol was also more common among women from the community organization than those from the STD clinic (34% vs. 22%). We observed no difference in reports of any sex in the last year without a condom, with 69% of women from the community organization and 71% of women from the STD clinic reporting this behavior (Table 2).
Sex with an IV drug user, self-reported IV drug use, sharing drug equipment, and transactional sex were reported rarely by men or women in either population.
STD prevalence
The prevalence of gonococcal infection, chlamydial infection, and a combined measure capturing GC or CT also differed between the two populations (Table 3). The prevalence of bacterial STDs was higher among STD clinic patients than among community organization patients in all subgroup analyses. Overall, STD clinic patients had GC prevalence of 7% and CT prevalence of 13%; community organization patients had GC prevalence of 1% and CT prevalence of 3%. CT was more prevalent in women than men in both populations, whereas GC was more prevalent in men than women in both populations. When considering the combined outcome of GC or CT infection, the overall prevalence among STD clinic patients reached nearly 1 in 5 (18%) whereas among community organization patients the prevalence of the combined outcome was 1 in 25 (4%) (Table 3).
Table 3.
Overall prevalence of GC, CT and GC or CT among individuals at a public STD clinic and a community AIDS service organization in a mid-western US city, 2009.
| Population | GC | CT | GC or CT | |||
|---|---|---|---|---|---|---|
|
| ||||||
| Prevalence | (95% CI a) | Prevalence | (95% CI a) | Prevalence | (95% CI a) | |
| Community organization | ||||||
| Men | 1.8 | (0.7, 3.8) | 2.6 | (1.2, 5.0) | 3.5 | (1.8, 6.1) |
| Women | 0.0 b | -- | 4.7 | (1.8, 10.0) | 4.2 | (1.8, 10.0) |
| Overall | 1.3 | (0.5, 2.8) | 3.4 | (2.0, 5.5) | 4.0 | (2.5, 6.2) |
| STD clinic | ||||||
| Men | 7.7 | (5.1, 11.0) | 12.3 | (9.0, 16.2) | 18.2 | (14.3, 22.7) |
| Women | 5.0 | (2.6, 8.5) | 13.3 | (9.3, 18.2) | 17.4 | (12.9, 22.8) |
| Overall | 6.6 | (4.7, 8.9) | 12.7 | (10.1, 15.6) | 17.9 | (14.9, 21.2) |
| Total | ||||||
| Men | 4.8 | (3.3, 6.6) | 7.5 | (5.7, 9.7) | 11.0 | (8.8, 13.6) |
| Women | 3.3 | (1.7, 5.6) | 10.3 | (7.4, 13.9) | 13.0 | (9.8, 16.9) |
| Overall | 4.2 | (3.1, 5.6) | 8.6 | (7.0, 10.4) | 11.8 | (9.9, 13.9) |
Abbreviations: STD = sexually transmitted disease; AIDS = acquired immune deficiency syndrome; GC = gonococcal infection; CT: chlamydial infection; CI = confidence interval.
Because of small cell sizes in some categories, all 95% confidence intervals around prevalence estimates computed using exact methods.
No positive GC cases among women at the community organization.
We also investigated combined GC/CT prevalence according to patients’ reports of exclusively same-sex (homosexual) encounters, opposite-sex (heterosexual) encounters, or bisexual encounters in the last year (“sex” included oral, vaginal or anal sex) (Table 4). Among male or female individuals with non-missing behavioral data who reported any sexual activity in the last year (n= 956), individuals at the STD clinic were much more likely than those at the community organization to report exclusively heterosexual encounters (85% of men and 89% of women at the STD clinic vs. 27% of men and 82% of women at the community organization). A substantial majority (67%) of men at the community organization reported only homosexual encounters in the last year. GC/CT prevalence was higher in every category among individuals at the STD clinic than those from the community organization, and was generally highest among those reporting exclusively heterosexual activity (5% for men and 7% for women at the community organization; 21% for men and 17% for women at the STD clinic) (Table 4). The exception was women at the STD clinic who reported bisexual encounters in the last year, who had GC/CT prevalence of 21%.
Table 4.
Prevalence of GC or CT infection, by gender and sexual behavior, among individuals at a public STD clinic and a community AIDS service organization in a mid-western US city, 2009.
| Population | Community organization | STD clinic | ||||
|---|---|---|---|---|---|---|
|
| ||||||
| n a | Prevalence | (95% CI d) | n a | Prevalence | (95% CI d) | |
| Only same-sex encounters | ||||||
| Men who report sex b with only men | 192 | 2.6 | (0.9, 6.0) | 39 | 5.1 | (0.6, 17.3) |
| Women who report sex with only women | 8 | 0.0 c | -- | 6 | 16.7 | (0.4, 64.1) |
| Only opposite-sex encounters | ||||||
| Men who report sex with only women | 77 | 5.2 | (1.4, 12.8) | 283 | 20.8 | (16.3, 26.1) |
| Women who report sex with only men | 85 | 7.1 | (2.6, 14.7) | 209 | 17.2 | (12.4, 23.0) |
| Bisexual encounters | ||||||
| Men who report sex with men and women | 16 | 0.0 c | -- | 11 | 0.0 c | -- |
| Women who report sex with men and women | 11 | 0.0 c | -- | 19 | 21.1 | (6.1, 45.6) |
Abbreviations: STD = sexually transmitted disease; AIDS = acquired immune deficiency syndrome; CI = confidence interval.
n is the total number in each population reporting this type of sexual behavior, independent of GC/CT status
In all measures, “sex” includes oral, vaginal and anal sex
No positive cases at the community organization among women reporting sex with men and women; among men reporting sex with men and women; or among women reporting sex with men and women. No positive cases at the STD clinic among men reporting sex with men and women.
Because of small cell sizes in some categories, all 95% confidence intervals around prevalence estimates were computed using exact methods.
Bivariate associations (Table 5)
Table 5.
Bivariate associations between selected demographic and risk characteristics and prevalence of GC or CT among individuals from a public STD clinic and a community AIDS service organization in a mid-western US city, 2009.
| Community organization | STD clinic | Total | ||||
|---|---|---|---|---|---|---|
| OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | |
| Gender | ||||||
| Male | 0.74 | 0.27, 2.00 | 1.06 | 0.69, 1.62 | 0.82 | 0.56, 1.21 |
| Female (referent) | 1. | -- | 1. | -- | 1. | -- |
| Race/Ethnicity | ||||||
| Black | 1.47 | 0.51, 4.23 | 1.26 | 0.77, 2.06 | 2.31 | 1.53, 3.49 |
| Other | (estimate not possible) a | 1.50 | 0.71, 3.15 | 2.16 | 1.10, 4.24 | |
| White (referent) | 1. | -- | 1. | -- | 1. | -- |
| Marital status | ||||||
| Divorced, separated or widowed | 0.56 | 0.07, 4.38 | 0.30 | 0.11, 0.85 | 0.36 | 0.14, 0.90 |
| Married | (estimate not possible) a | 0.24 | 0.06, 1.02 | 0.27 | 0.06, 1.11 | |
| Single (referent) | 1. | -- | 1. | -- | 1. | -- |
| Education | ||||||
| High school/GED or more | 0.31 | 0.11, 0.83 | 0.74 | 0.48, 1.15 | 0.50 | 0.34, 0.74 |
| Less than high school (referent) | 1. | -- | 1. | -- | 1. | -- |
| Age | ||||||
| <23 years | 2.37 | 0.82, 6.85 | 4.64 | 2.52, 8.55 | 4.02 | 2.39, 6.76 |
| 23–30 years | 0.49 | 0.12, 1.97 | 3.17 | 1.72, 5.84 | 2.24 | 1.32, 3.81 |
| >30 years (referent) | 1. | -- | 1. | -- | 1. | -- |
| Number of sex partners in last year | ||||||
| 6+ partners | 0.91 | 0.12, 6.59 | 3.29 | 1.57, 6.89 | 1.62 | 0.84, 3.10 |
| 2–5 partners | 2.35 | 0.51, 10.72 | 1.52 | 0.88, 2.64 | 1.55 | 0.93, 2.57 |
| 0–1 partners (referent) | 1. | -- | 1. | -- | 1. | -- |
| Sex b in the last year with an HIV-positive person | ||||||
| Yes | (estimate not possible) a | 0.91 | 0.11, 7.88 | 0.24 | 0.03, 1.76 | |
| No (referent) | 1. | -- | 1. | -- | ||
| Sex in the last year with a person of unknown HIV status | ||||||
| Yes | 1.03 | 0.37, 2.90 | 0.79 | 0.39, 1.61 | 0.52 | 0.30, 0.90 |
| No (referent) | 1. | -- | 1. | -- | 1. | |
| Sex in the last year with an anonymous partner | ||||||
| Yes | 0.41 | 0.09, 1.83 | 1.33 | 0.69, 2.56 | 0.70 | 0.40, 1.24 |
| No (referent) | 1. | 1. | -- | 1. | -- | |
| Sex in the last year without a condom | ||||||
| Yes | 2.00 | 0.63, 6.30 | 1.85 | 1.10, 3.13 | 2.13 | 1.33, 3.40 |
| No (referent) | 1. | -- | 1. | -- | 1. | -- |
| Sex in the last year with a man | ||||||
| Overall | ||||||
| Yes | 0.63 | 0.21, 1.86 | 0.68 | 0.44, 1.05 | 0.48 | 0.33, 0.71 |
| No (referent) | 1. | -- | 1. | -- | 1. | -- |
| Among men | ||||||
| Yes | 0.36 | 0.10 1.27 | 0.16 | 0.04, 0.66 | 0.13 | 0.06, 0.28 |
| No | 1. | -- | 1. | -- | 1. | -- |
| Among women | ||||||
| Yes | (estimate not possible) a | 1.70 | 0.21, 14.00 | 3.14 | 0.41, 24.06 | |
| No | 1. | -- | 1. | -- | ||
| Sex in the last year with a woman | ||||||
| Overall | ||||||
| Yes | 0.83 | 0.26, 2.63 | 1.36 | 0.88, 2.10 | 1.74 | 1.19, 2.56 |
| No (referent) | 1. | -- | 1. | -- | 1. | -- |
| Among men | ||||||
| Yes | 1.40 | 0.39, 5.09 | 2.66 | 0.92, 7.72 | 4.43 | 2.23, 8.82 |
| No | 1. | -- | 1. | -- | 1. | -- |
| Among women | ||||||
| Yes | (estimate not possible) a | 1.22 | 0.43, 3.47 | 0.79 | 0.29, 2.11 | |
| No | 1. | -- | 1. | -- | ||
| Sex in the last year while using alcohol or drugs | ||||||
| Yes | 1.27 | 0.46, 3.49 | 0.79 | 0.49, 1.28 | 0.76 | 0.50, 1.16 |
| No (referent) | 1. | -- | 1. | -- | 1. | -- |
Abbreviations: STD = sexually transmitted disease; AIDS = acquired immune deficiency syndrome; OR = odds ratio; CI = confidence interval; GED = general equivalency diploma
OR not able to be estimated because of one or more 0 cell sizes
In all measures, “sex” includes oral, vaginal and anal sex
Among individuals at the community organization, the only factor significantly associated with decreased odds of GC/CT infection was higher education (odds ratio (OR): 0.31, 95% CI: 0.11, 0.83). Among individuals from the STD clinic, several characteristics were significantly associated with GC/CT prevalence. Being divorced, separated or widowed (vs. being single) and being a man who had sex with a man in the last year were both associated with lower odds of GC/CT. Being younger, reporting at least six sexual partners in the past year, and having sex without a condom in the last year were all significantly associated with increased odds of GC/CT among individuals at the STD clinic (Table 5).
When participants from the community organization and the STD clinic were combined, several of these population-specific associations persisted. In addition, new associations emerged: being black or of ‘other’ race (vs. white race) and being a man who reported any sex in the last year with a woman were both significantly associated with increased odds of GC/CT in the combined population. Men who reported any sex in the past year with a man or with a person of unknown HIV status had decreased odds of GC/CT in the combined population (Table 5).
Gender, sex in the last year with an HIV-positive person, sex in the last year with an anonymous partner, and sex in the last year while using alcohol or drugs were not associated with odds of GC/CT in individuals from the community organization, the STD clinic, or the combined population.
DISCUSSION
Our analyses documented CT prevalence of 13% and GC prevalence of 7% among men and women seeking care at a public, urban STD clinic in a mid-western US city. In contrast, the prevalence at a community-based AIDS service organization was much lower: 3% for CT and 1% for GC. Prevalence in the STD clinic population is roughly similar to what has been observed in public STD clinics in other US cities. Among male and female patients seen in Baltimore’s STD clinics between 2004 and 2007, CT prevalence was 1% and GC prevalence was 12%.14 Among patients identifying as men who have sex with men (MSM) at a municipal STD clinic in San Francisco in 2003, the prevalence of urethral CT was 5% and urethral GC was 6%.15 The figures for our community-based cohort are also similar to those detected in other settings. GC prevalence among men screened through community-based organizations in Baltimore, Denver, San Francisco and Seattle was 1.4%. 16
The most recent assessments of gonococcal and chlamydial infection in the same mid-western city are nearly twenty years old. A study using data collected in 1991 through a gonococcal screening program among 44,366 women aged 14 to 44 years found overall GC prevalence of 1.8%. The factors most strongly associated with GC were young age, unmarried marital status, and the population prevalence of GC at each clinical screening site. The prevalence of gonococcal infection among women in the sample ranged from 0.1% for married women over 25 years of age at low-prevalence provider sites to 7.8% in unmarried women under age 20 at high-prevalence sites.17 The same authors separately analyzed a community-wide chlamydia screening effort among women at more than 50 provider sites. That analysis assessed trends in chlamydial prevalence from 1989 to 1992 and reported a 33% decline in prevalence during the screening period (from 8.0% in 1989 to 5.4% in 1992).18 Although the decline was considerable, the characteristics associated with chlamydial infection remained unchanged: young age, black race, and unmarried marital status.18 Nearly two decades later, the present analyses confirm the previous findings, with young age, black race and unmarried marital status among the most significant predictors of GC/CT in our combined population.
Our findings underscore the importance of careful interpretation of the intersection of risk factors such as gender and sexual orientation. Overall, GC/CT prevalence was similar between men and women (11% and 13%, with considerable confidence interval overlap). However, among men who reported only sex with men in the last year, GC/CT prevalence was substantially lower: 5% at the STD clinic and 3% at the community organization. In contrast, GC/CT prevalence was considerably higher among men who reported only sex with women in the last year: 21% at the STD clinic and 5% at the community organization. Similarly complex is our finding that overall, sex with a man in the last year was significantly protective against GC/CT, while sex with a woman was significantly harmful. When these results are further stratified by respondent gender, however, the overall protective effect of sex with men vanishes for women and is strengthened for men, and the overall harmful effect of sex with women also vanishes for women and is strengthened for men. Interestingly, the highest prevalence subgroup in our analysis was women at the STD clinic who reported sex with both men and women in the past year (GC/CT prevalence of 21%). The pattern suggested by this finding is similar to a recent analysis of the nationally-representative National Health and Nutrition Examination Surveys (NHANES), in which the seroprevalence of herpes simplex virus type 2 was highest (45.6%) among women who self-identify as heterosexual but also report some female lifetime partners.19–20
Our analyses have some important limitations. Our GC/CT findings are based on nucleic acid amplification testing of urine samples. While NAAT is highly sensitive and specific for detecting gonococcal and chlamydial infections, the use of urine samples means that our prevalence statistics capture urethral infections. GC/CT prevalence as detected through urine samples alone may underestimate the overall prevalence we might have seen had we tested other anatomical sites. For women, endocervical swab specimens have similar sensitivity and specificity to urine specimens for both GC and CT.21 However for populations such as MSM practicing rectal sex, detection of only urethral GC/CT likely misses a substantial number of those with rectal and/or pharyngeal infections. One assessment of MSM patients which tested rectal, urethral, and pharyngeal specimens found that 53% of CT infections and 64% of GC infections were at non-urethral sites.15 This limitation could add further complexity to the finding that, among men, having sex with a man was strongly protective against GC/CT in the STD clinic and combined populations. We are currently abstracting data on MSM patients who received both rectal GC and CT cultures at the STD clinic and NAAT on urine specimens from January through June 2010 in order to better characterize the overall GC/CT prevalence in this population; unfortunately, that type of data was not available for the current analysis. Our outcome measures are similarly limited in that we were able to assess only GC and CT outcomes; we lack data on syphilis infection and HIV status (except as reported by participants on self-administered clinic forms).
Another limitation in our analysis is that the behavioral data is self-reported; previous examinations of self-reported sexual behavior data have found varying levels of validity and reliability.22–23 Because the days when outreach occurred at the community organization were not random (usually falling on a Tuesday or Wednesday), the analysis population may reflect distinct trends in patients’ care-seeking behavior. As a result our findings may not be generalizable to patients not able to attend the clinic during these days of the week. These data are cross-sectional, and associations can only be interpreted as correlations without causal inference. Finally, 8% of records were missing behavioral data on sexual risk factors. Those with missing data were more likely to be from the community organization than the STD clinic (87% of those with missing behavioral data vs. 44% in the overall population were from the community organization), and consequently less likely to be black (19% of those missing behavioral data vs. 42% overall), and less likely to have GC or CT (5% of those missing behavioral data vs. 12% overall). Transgendered individuals (n=3, 0.3% of the total analysis population) were also excluded from gender-specific results.
Our data represent a random sample of individuals seeking services at the STD clinic and a convenience sample of individuals seeking HIV testing at the community organization; our results confirm that STD prevalence differs widely by sexual practices, population group and the intersection of gender with these factors. The generalizability of our results to other population groups in this city is not known (e.g., those seeking care from private physicians, individuals with asymptomatic disease who fail to seek STD testing, transgendered individuals, etc.). Given the considerable differences in demographic characteristics, behavioral factors and STD rates between the two groups, local approaches to STD control should also be carefully targeted to specific subpopulations: to those with lower educational attainment in the community organization population and to unmarried young people with high numbers of sexual partners and low condom use in the STD clinic population. Interestingly and despite extraordinary racial disparity in STD rates in other parts of the country – a 2007 report on GC among 15- to 19-year old women in California found rates 20 times higher for black women than for whites 24 – in our analysis, black race was not significantly associated with the increased odds of GC/CT in either the community organization nor the STD clinic. Only when these groups were combined did race emerge as a significant predictor, and the magnitude of the association (OR: 2.31, 95% CI: 1.53 to 3.49) was much lower than has been reported in other US populations. Nevertheless, we note with disappointment that the risk factors associated with GC/CT prevalence among women nearly 20 years ago are very similar to those which emerged in our analysis. These findings serve as an updated baseline assessment of GC/CT prevalence in two populations in this mid-western US city, and are critical for the development of future targeted screening and prevention interventions.
Footnotes
Financial disclosure: No author has any relevant financial relationships to disclose.
Contributor Information
Abigail Norris Turner, Email: ant@osumc.edu.
Deanna Flynn, Email: flynn.107@buckeyemail.osu.edu.
Merry Krempasky, Email: merryk@Columbus.gov.
Karen Fields, Email: KSFields@columbus.gov.
Wynette Collins, Email: wynettec@columbus.gov.
Melissa Ervin, Email: mervin@Columbus.gov.
Peggy Anderson, Email: peggyanderson@catf.net.
Tania Peterson, Email: TaniaSlack@catf.net.
Mysheika LeMaile-Williams, Email: MRLeMaile-Williams@columbus.gov.
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